1. Field of the Invention
This invention relates to the enhanced biodegradation of hydrocarbons in soils and water. More particularly, this invention relates to a process for increasing the rate of biodegradation of hydrocarbons in soils and water by amending the soil or water with a surfactant-fertilizer compound.
2. Description of Related Information
Hydrocarbons such as crude petroleum and petroleum-derived products are complex mixtures of straight and branched-chain alkanes and alkenes, saturated ring compounds, and aromatic compounds. Small amounts of sulfur, nitrogen, or oxygen can also be covalently attached to these various hydrocarbon compounds. Gasoline, kerosene, burner fuel oil, diesel oil, gas turbine oil, and aviation fuel are examples of petroleum-derived fuel oils, distillates, or catalytically processed petroleum fractions widely used by industry. Unfortunately, a side effect of this widespread use is the contamination of the environment, resulting from spillage, seepage, or accidental release of petroleum derived hydrocarbons.
In the past, a generally accepted procedure for controlling possible environmental damage of hydrocarbon-contaminated soil involved permanent removal of the contaminated soil to a secure landfill. However, the decreasing availability of landfills which can accept hazardous wastes, the high cost of excavation and transportation of soil from hydrocarbon-contaminated sites, and the potential liability exposure associated with off-site transport and disposal, have made landfill disposal of hydrocarbon-contaminated soil an increasingly unattractive means for handling hydrocarbon-contaminated soils.
An alternative procedure for cleaning hydrocarbon-contaminated soils is known as bioremediation. Bioremediation is a natural process which provides for the degradation of hydrocarbonaceous contaminants by biologic materials, such as bacteria, saprophytes, fungi, protozoa, bacterial enzymes, or saprophytic enzymes, to carbon dioxide, water and more cell biomass. These hydrocarbon degrading microorganisms are often naturally present, i.e., indigenous, in contaminated soils, and, given sufficient time, they can naturally degrade the hydrocarbon contaminants. The bioremediation of hydrocarbon-contaminated soils is favored over soil removal or chemical treatment of soil, for several reasons, including lower cost and the ability for on-site reduction of hydrocarbon contamination.
The advantages of bioremediation can be outweighed, however, by the substantial length of time required to bioremediate by means of indigenous microorganisms: even under optimum conditions, months or years may be required to reduce the levels of hydrocarbon contamination of soils to a desired level. This disadvantage has greatly limited the use of bioremediation to reduce hydrocarboncontaminated environments.
It would be useful to decrease the time required for the bioremediation of a contaminated site. It is already well-known that certain environmental conditions are important factors in microbial growth and activity, and therefore affect the rates at which biodegradation occurs. Two parameters which directly effect biodegradation are: a) the availability of nitrogen to the microbiota; and b) the availability of the contaminating substrate to the microbiota. These parameters are often difficult to change and/or deliver in an in-situ soil environment. For example, it is known to add nitrogen, in the form of a fertilizer, to the soil to enhance the growth of the microbiota, but it is often difficult to achieve a good physical distribution of the nitrogen. One method for enhancing the distribution of the added fertilizer is to use an aqueous solution containing fertilizer and a surfactant. The surfactant makes it easier for the fertilizer to distribute through the contaminated soil, and has the added benefit of enhancing the contact of the microbiota with the contaminant. A problem with this method is that when the fertilizer and the surfactant are applied, however, they tend to differentially partition and distribute unevenly in the contaminated soil. This reduces the availability of the fertilizer to the indigenous microbiota.
It would be desirable, therefore, to provide fertilizer and a surfactant to contaminated soil in a manner such that the fertilizer and surfactant do not differentially partition and distribute unevenly. The present invention directly addresses the shortcomings of natural bioremediation and bioremediation enhanced by the simple addition of a mixture of fertilizer and surfactant by providing a surfactant-fertilizer molecule which, when introduced into a contaminated matrix, does not differentially partition, provides greater distribution of the fertilizer, provides greater contact between the microbiota and the contaminant and increases the rate of hydrocarbon contaminant degradation.